Dynamics of local extreme rainfall of super Typhoon Soudelor (2015) in East China     

Jinsong Pan  Daigao Teng  Fuqing Zhang  Lingli Zhou  Ling Luo  Yonghui Weng  Yunji Zhang 《中国科学:地球科学(英文版)》2018,61(5):572-594

The characteristics and dynamics associated with the distribution, intensity, and triggering factors of local severe precipitation in Zhejiang Province induced by Super Typhoon Soudelor (2015) were investigated using mesoscale surface observations, radar reflectivity, satellite nephograms, and the final (FNL) analyses of the Global Forecasting System (GFS) of the National Center for Environmental Prediction (NCEP). The rainfall processes during Soudelor’s landfall and translation over East China could be separated into four stages based on rainfall characteristics such as distribution, intensity, and corresponding dynamics. The relatively less precipitation in the first stage resulted from interaction between the easterly wind to the north flank of this tropical cyclone (TC) and the coastal topography along the southeast of Zhejiang Province, China. With landfall of the TC in East China during the second stage, precipitation maxima occurred because of interaction between the TC’s principal rainbands and the local topography from northeastern Fujian Province to southwestern Zhejiang Province. The distribution of precipitation presented significant asymmetric features in the third stage with maximal rainfall bands in the northeast quadrant of the TC when Soudelor’s track turned from westward to northward as the TC decayed rapidly. Finally, during the northward to northeastward translation of the TC in the fourth stage, the interaction between a mid-latitude weather system and the northern part of the TC resulted in transfer of the maximum rainfall from the north of Zhejiang Province to the north of Jiangsu Province, which represented the end of rainfall in Zhejiang Province. Further quantitative calculations of the rainfall rate induced by the interaction between local topography and TC circulation (defined as “orographic effects”) in the context of a one-dimensional simplified model showed that orographic effects were the primary factor determining the intensity of precipitation in this case, and accounted for over 50% of the total precipitation. The asymmetric distribution of the TC’s rainbands was closely related to the asymmetric distribution of moisture resulted from changes of the TC’s structure, and led to asymmetric distribution of local intense precipitation induced by Soudelor. Based on analysis of this TC, it could be concluded that local severe rainfall in the coastal regions of East China is closely related to changes of TC structure and intensity, as well as the outer rainbands. In addition, precipitation intensity and duration will increase correspondingly because of the complex interactions between the TC and local topography, and the particular TC track along large-scale steering flow. The results of this study may be useful for the understanding, prediction, and warning of disasters induced by local extreme rainfall caused by TCs, especially for facilitating forecasting and warning of flooding and mudslides associated with torrential rain caused by interactions between landfalling TCs and coastal topography.  相似文献   

不同环流形势下浙江中西部地区强对流的诊断预报方法          下载免费PDF全文

毛程燕  郑倩  龚理卿  荆思佳  李浩文 《气象科学》2021,41(5):687-695

基于地面观测和探空资料、NCEP／NCAR 1°×1°再分析资料，利用中尺度分析技术，对2008—2018年暖季（4—10月）发生在浙江中西部地区（简称浙中西）的65次强对流天气过程进行天气形势配置，得到发生在浙中西的雷暴大风、冰雹、短时强降水及混合性强对流的规律特征。结果如下：（1）浙中西强对流天气出现的大尺度环流有5种基本流型配置：干冷气流型（6.2%）、锋生切变型（13.8%）、暖湿气流型（38.5%）、副高边缘型（30.7%）、台风外围型（10.8%），并给出了每种概念模型下的主要物理机制和中尺度特征。（2）分析了不同概念模型下典型强对流天气个例，简要归纳出各种流型下的主要系统配置和演变规律，并将抽象的概念模型应用到实际预报分析中。（3）分析不同流型下强对流的阈值范围，如干冷气流型I_w大风指数平均为26.1 m·s^-1，850 hPa与500 hPa温差可达27.5℃，500 hPa相对湿度平均只有15％等，提炼出相似环流形势下不同强天气的主要预报指标，为强对流预报提供量化参考。  相似文献   

极端天气预报指数和集合异常预报法在浙江台风和梅雨暴雨预报中的应用北大核心          下载免费PDF全文

王丽颖  娄小芬  罗玲  钱浩 《气象科学》2023,43(1):25-35

利用2016—2021年ECMWF集合预报,评估了极端天气指数EFI(Extreme Forecast Index)、尾偏移指数SOT(“Shift of Tail”index)以及集合异常预报法在浙江台风和梅雨暴雨预报中的应用效果。通过研究极端天气预报指数对浙江台风和梅雨暴雨的最优预报阈值,发现梅雨暴雨阈值比台风暴雨明显偏小,且随预报时效增加减小速度偏慢。最优阈值预报相比确定性模式预报,在台风和梅雨暴雨预报检验中体现出更好的稳定性、提前性和准确性。进一步研究发现,通过区分天气类型确定的最优预报阈值,可作为台风和梅雨暴雨落区预报的参考依据。925 hPa水汽通量散度的集合异常度对浙江台风暴雨的落区和强度变化有较好的预报效果,850 hPa涡度和700 hPa垂直速度的集合异常度可以反映稳定性梅雨暴雨的过程演变。  相似文献   

ECMWF极端天气指数在华东台风 降水预报中的应用和检验          下载免费PDF全文

傅良  罗玲  张玉静  娄小芬  钱浩 《气象科学》2022,42(2):182-192

选取2015—2018年影响华东地区的13个台风个例,分析降水极端天气指数EFI (Extreme Forecast Index)和SOT (Shift of Tails)与台风降水之间的统计关系。结果表明:EFI和SOT与降水气候百分位之间存在明显的正相关关系。EFI和SOT越大,强降水发生概率越高。随着预报时效的增加,EFI和SOT指数对暴雨和大暴雨的预报效果逐渐变差。对于短期(72 h以内的时效),EFI预报技巧优于SOT,而随着预报时效的延长,SOT的预报技巧逐渐接近并超过EFI。以TS评分最大为标准兼顾合理的预报偏差,得到两种极端天气指数不同预报时效、不同等级暴雨的预报阈值。总体而言,事件越极端,EFI和SOT的预报阈值越大,对于暴雨和大暴雨,EFI指数的预报阈值随着预报时效的延长有减小趋势,而SOT的预报阈值基本保持不变。在台风极端降水预报中,EFI和SOT可以作为EC定量降水预报的补充,有助于减少强降水的漏报,并提早发出预警信息。  相似文献   

浙东地形对台风“利奇马”极端降水的影响分析          下载免费PDF全文

王凯  齐铎  高丽  翁之梅 《气象科学》2021,41(2):162-171

利用自动站实时降水资料、NCEP再分析资料和多普勒雷达资料,结合中尺度数值模式WRF对台风"利奇马"在浙东地区产生的极端降水过程进行分析,重点研究了浙东地形对极端降水的影响。结果表明,"利奇马"影响期间,浙东强降水过程出现2个雨量峰值,依次由台风外层螺旋云带和台风中心附近的多个中尺度对流云团持续影响所造成,浙东地形对这一系列对流云团有明显的加强作用。浙东地区西部山脉对"利奇马"有阻滞和辐合抬升两方面作用,前者通过地形阻挡拖曳,延长强降水时长,后者通过山前显著的动力抬升作用和水汽辐合加强造成降水增幅。根据估算可知,括苍山脉在强降水阶段对暴雨的增幅可达11 mm·h~(-1),接近此时段内总雨量的2.5成。通过敏感性试验降低地形高度后,浙东地区辐合及上升运动减弱,雨量也明显减少,进一步验证了浙东地形是造成此次极端降水事件的重要原因。  相似文献   

组合表面Bragg散射模型共极化SAR海表面风速反演          下载免费PDF全文

方贺  杨劲松  樊高峰  李超  史达伟  William Perrie 《遥感学报》2022,26(6):1274-1287

组合表面布拉格散射模型CSBS（Composite Surface Bragg Scattering）由布拉格（Bragg）散射模型和几何光学模型组成，是海洋微波散射的经典模型，可用于星载合成孔径雷达SAR（Synthetic Aperture Radar）海表面风场反演。研究指出，Bragg散射模型仅适用于中等入射角条件，几何光学模型则更适用于小入射角情形。然而，如何确定中等和小入射角的阈值，即CSBS模型最优入射角的选取目前尚无定论。基于142景成像于美国东西海岸和中国东海的RADARSAT-2精细四极化SAR影像数据和海洋浮标数据，本文提出了一种最优局地入射角查找算法，分别对VV和HH极化SAR数据进行最优入射角阈值的选取。结果显示，局地入射角14°和16°分别为VV和HH极化影像CSBS模型反演风速最优入射角。基于最优入射角的选取，本文在0—15 m/s海况区间内利用CSBS模型对VV和HH极化SAR影像开展风速反演实验，并将反演风速与浮标风速进行对比。结果显示，基于VV和HH极化数据的CSBS模型反演风速与浮标风速均方根误差分别为2.15 m/s和2.32 m/s，相关系数分别为0.79和0.75，两者具有良好的一致性。本文研究结论表明基于最优入射角设置后的CSBS模型在海面风速小于15 m/s条件下具有良好的应用性，后续研究将更加关注CSBS模型在高海况以及交叉极化SAR数据情况下的应用。  相似文献